1. Field of Invention
This invention relates generally to a UV lamp rack assembly for use in ultraviolet ray water and wastewater treatment systems, and more particularly to a modular assembly in which a vertical array of UV lamp units is supported on a rack, each unit being separately removable from the rack without disturbing the other units.
2. Status of Prior Art
Chlorination has heretofore been the most commonly used technique for disinfecting large quantities of wastewater. Chlorination involves the addition of small amounts of chlorine or chlorine compounds to the water to destroy undesirable microorganisms. A disadvantage peculiar to disinfection of the effluent of a wastewater treatment plant by chlorination is that such disinfection leaves a residual. This residual can be environmentally harmful, or undesirable should the body of water receiving the chlorinated discharge be reused for drinking waster. Other factors that must be taken into account are the hazards associated with transporting and storing chlorine in populated areas.
While in the specification we shall deal with the treatment of effluent from a wastewater treatment plant, it is to be understood that there are many other practical applications for the invention, such as in the disinfection of environmental, industrial and commercial waters.
The disadvantages of chlorination are absent in disinfection by ultraviolet radiation, for no chemicals are involved in this sterilization technique. Ultraviolet (UV) radiation at certain wavelengths has powerful germicidal properties, as a consequence of which the use of UV radiation for purposes of wastewater disinfection has been gaining rapidly in popularity. In a typical UV disinfection system, a source of ultraviolet radiation such as a bank of ultraviolet lamps is housed in a chamber through which the liquid to be treated is caused to flow, the liquid being subjected to UV radiation in the course of its passage through the chamber.
One such prior art UV disinfection arrangement is disclosed in the Ellner U.S. Pat. No. 3,948,772, in which a battery of parallel elongated ultraviolet lamps is supported on carrier frames in a water flow channel. The spacing of the lamps from each other and from the walls of the channel is such as to subject all of the water to the sterilizing effects of ultraviolet radiation.
Because ultraviolet lamps producing ultraviolet radiation of a suitable wavelength, typically 2540 Angstroms, have a limited life, provision must be made to replace a lamp when it has failed. By failure is meant not only a lamp that is altogether inoperative, but one whose level of radiation has fallen to an unacceptable degree. One approach to UV lamp replacement is disclosed in the Maarschalkeweerd U.S. Pat. No. 4,482,809, in which groups of vertically adjacent lamps are supported in individual rack assemblies which can be withdrawn from a treatment channel for replacement of the lamps.
In the arrangement described in the Maarschalkeweerd patent, the lamps are housed in transparent quartz tubes extending between sockets integral with the side arms of a rigid frame, at least one of the sockets having an end plug through which a lamp can be withdrawn longitudinally once the frame has been withdrawn from the channel. This arrangement is relatively complex to fabricate. And while it may appear to be advantageous that the lamps are rigidly secured to the frame, in practice any distortion of the frame during handling will strain the quartz tubes containing the lamps, thereby risking breakage.
In the removable lamp arrangement disclosed in the Latal et al. U.S. Pat. No. 4,825,083, individual ultraviolets lamp units are loosely and retractably located within frames supported in a water treatment channel. Individual frames supporting arrays of parallel lamp units may be removed from the channel, and the lamp units may be individually disengaged from the frame and disassembled for lamp replacement. The frames have unitary plug connectors so arranged that the plug of a frame must be disengaged from the power supply before that frame can be removed from the channel.
None of the prior art arrangements for the UV treatment of water by means of a bank or array of UV lamp units supported on a frame or rack make it possible manually to remove a particular lamp unit from the rack without difficulty, without in any way disturbing the other units and without the need for special tools.